Editor’s note: This article was written by Denise-Marie Ordway with The Journalist’s Resource.
This column continues the discussion on the longstanding problems associated with the poor indoor air quality in schools in the United States.
Read more about these findings below as well as links to other useful resources.
How common is mold and other types of indoor air pollution?
Asthma Prevalence and Mold Levels in US Northeastern Schools
Evin J. Howard, et al. Journal of Allergy and Clinical Immunology: In Practice, March 2021.
Researchers analyzed dust samples collected from 32 schools in densely populated areas in the northeastern U.S. and found they contained several types of mold. They also discovered mold levels in classroom dust often exceeded levels of mold found in dust collected from local homes.
Researchers tested samples taken from a total of 114 classrooms and the bedrooms and living rooms of 33 homes from 2014 through 2018. They tested for 30 types of mold, 26 of which are associated with water damage and 10 of which are associated with outdoor sources.
Classrooms also had higher levels of these molds, associated with outdoor sources: alternaria alternata, cladosporium cladosporioides 1, cladosporium cladosporioides 2, cladosporium herbarum, epicoccum nigrum and penicillium chrysogenum.
For most remaining mold types, differences were not statistically significant.
When the researchers looked for links between mold levels and rates of asthma among schoolchildren living in the area, they found asthma was most common in schools with higher levels of outdoor mold — the kind found in soil and on leaf surfaces, for example.
“Therefore, the differences in the prevalence of asthma was not indicative of any significant differences in mold growth resulting from water-damage indoors but rather factors associated with the increased levels of molds from outside entering and accumulating in the schools,” the researchers write, adding that 30 of the 32 schools studied did not have air conditioning.
“In addition to AC, the frequency of window and door opening could also affect the levels of (outdoor) molds,” they write. “Cleaning frequency and thoroughness could also affect the build-up of (outdoor) molds inside schools.”
Association Between Allergen Exposure in Inner-City Schools and Asthma Morbidity Among Students
William J. Sheehan, et al. JAMA Pediatrics, January 2017.
This study, which also focuses on the northeastern U.S., found high levels of mouse allergen in 37 elementary schools. It concludes that children with asthma exposed to high levels of mouse allergen, which is present in the urine, hair and dander of mice, were more likely to experience increased asthma symptoms and poorer lung function.
Researchers analyzed samples of dust taken from the classrooms and bedrooms of 284 students, aged 4 to 13 years, who had been diagnosed with asthma and attended one of the 37 elementary schools from March 1, 2008, to Aug. 31, 2013. Researchers tested for allergens associated with mice, rats, dogs, cats, cockroaches and dust mites.
Mouse allergen was most prevalent. It was detected in 99.5% of school samples and 96% of home samples. However, mouse allergen levels were higher in schools than in homes.
Cat, dog and dust mite allergens also were common in schools and homes, although at much lower levels. For example, researchers found cat allergen in 94.8% of school samples and 79.4% of home samples. Allergens from cockroaches and rats “were mostly undetectable” in both locations, the researchers write.
They note that allergen levels and the types of allergens present in schools differ according to the climate of the area.
“In the inner-city schools in our study, mouse allergen was the predominant exposure, whereas levels of cockroach, pet, and dust mite allergens were undetectable or low,” they write. “In contrast, other cities with warmer climates and different building conditions have demonstrated high levels of school cockroach allergen. The low levels of dust mites and cockroach in our study are likely owing to the long, dry, and very cold winters in the studied region, as these pests require humidity and warmth to survive.”
Classroom Indoor PM2.5 Sources and Exposures in Inner-City Schools
Aleshka Carrion-Mattaa, et al.Environment International, October 2019.
For this study, researchers went into 32 schools in densely populated areas in the Northeast to measure airborne levels of fine particulate matter with diameters of 2.5 micrometers or smaller (PM2.5). Prior research has found this type of air pollution is associated with cognitive impairment and exacerbated asthma.
Researchers analyzed PM2.5 levels inside schools each fall, winter and spring from 2009 to 2013 and compared them to outdoor levels. They learned that indoor and outdoor concentrations of PM2.5 were comparable, “demonstrating penetration of outdoor pollution to indoors.” They also learned PM2.5 levels inside schools varied by season and contained a range of pollutants from automobiles, roads, soil, burning vegetation and other sources.
Pollution from motor vehicles was greatest during the fall and winter, the researchers write.
“Activities in the school environment during winter such as using motor equipment/vehicles to clean the snow and spreading salt, and during the fall such as cleaning the leaves may have driven these differences to the other sources,” they explain. “In addition, higher contribution of biomass burning in winter is more likely associated with wood burning at the neighborhood of schools.”
Of the 32 schools studied, four had air conditioning systems, 15 had radiant heat “natural ventilation” and the rest had either classroom-based vents or a combination of ventilation types.
Indoor air quality and child health and student performance
Indoor Air Quality and Health in Schools: A Critical Review For Developing the Roadmap for the Future School Environment
Sasan Sadrizadeh, et al. Journal of Building Engineering, October 2022.
This paper summarizes 50 years of classroom air quality research conducted in 40 countries across six continents, concluding that various pollutants pose severe risks to student health.
Indoor air quality in schools “is characterized by a complex of contaminants,” including molds, bacteria, volatile organic compounds, particulate matter, and trace metals from road traffic, the researchers write. They note that several studies have found that levels of certain airborne pollutants were higher inside schools than in homes and commercial buildings.
“Inhalation exposure to air pollution has increased children’s mortality rate, acute respiratory disease, and asthma,” they write. “Due to different responses of the children’s immune systems to indoor air exposures, various chronic diseases and symptoms have been reported and characterized as ‘sick building syndrome.’”
This paper is based on a review of 304 reports and research papers published between 1970 and 2022. It offers a broad overview of research examining types of pollutants. It finds, for example, that volatile organic compounds — a group of chemicals used in finishing and furnishing — are one of the most dangerous pollutants found in classroom air.
“Construction materials, furnishings such as desks and shelves, resins of wood products, adhesives, glues, paints, cleaning chemicals, and carpets are primary [volatile organic compounds] emission sources in schools,” the researchers write. “The VOC concentrations in newly built or recently renovated school buildings may be significantly higher than ordinary ambient levels.”
The paper also discusses factors that influence levels of pollution inside schools such as ventilation, temperature, outdoor wind speeds and classroom cleaning protocols.
The researchers point out that research demonstrates a link between indoor air quality and student achievement. Studies “confirm that poor air quality affects both typical schoolwork of pupils, i.e. performance in simple learning tasks such as math and language exercises and pupils’ examination grades and end-of-the-year results,” they write.
Does Dampness and Mold in Schools Affect Health? Results of a Meta-Analysis
William J. Fisk, Wanyu R. Chan and Alexandra L. Johnson. Indoor Air, November 2019.
While research suggests students are at an increased risk of developing respiratory issues when dampness and mold are present in schools, renovations aimed at eliminating dampness and mold do not always alleviate such health problems, according to this Berkley Lab analysis.
To better understand the health conditions associated with mold and dampness in schools, researchers combined and analyzed data they collected from 11 studies of the issue published between 1995 and 2016. What they learned: The evidence most strongly suggests that coughing, wheezing and nasal symptoms are associated with mold and dampness in schools.
When the Berkley Lab researchers reviewed four other studies on renovations to correct dampness and mold in schools, they found mixed results. One of those studies reported improvements in some — but not all — student health symptoms after a thorough renovation was completed. For example, there was not a statistically significant change in the number of student complaints about headaches. That study, which focuses on four schools in Finland, also found that “a partial renovation did not significantly improve health.”
Berkley Lab researchers note that efforts to reduce dampness and mold might be more successful is there were generally accepted criteria for distinguishing problematic levels of dampness and mold.
“Ideally, school districts seeking to reduce dampness and mold in their buildings would have clear criteria defining the dampness and mold conditions that trigger remedial actions,” the researchers write. “However, the various studies cited have employed a variety of definitions for dampness and mold and there are no generally accepted criteria for distinguishing a problematic level of dampness and mold, which adversely affects health, from a non-problematic level of dampness and mold.”
Association between Traffic-Related Air Pollution in Schools and Cognitive Development in Primary School Children: A Prospective Cohort Study
Jordi Sunyer, et al. PLOS Medicine, March 2015.
Children who attended schools in parts of Barcelona, Spain where there were high levels of automobile traffic pollution showed less progress on cognitive exams than did children attending schools where traffic pollution was low, this study finds.
For example, students in more polluted areas demonstrated a 7.4% increase in working memory over the course of a year, on average. Meanwhile, students in less polluted areas showed an average increase of 11.5%.
Researchers note there also were gender-based differences.
“Boys appeared more susceptible to air pollution, although both boys and girls showed an adverse association of school air pollution with cognitive development,” they write. “Although results could be due to chance, in animals, males were more susceptible to airborne metals than females, which may be because of sex-specific altered dopamine function.”
Thirty-nine schools participated in the study. A combined 2,715 students aged 7 to 10 years took computerized tests every three months for a year so researchers could measure their inattentiveness and development of working memory.
The researchers also collected data on levels of three types of pollutants — carbon, nitrogen dioxide and ultrafine particles — present inside classrooms and outside in school courtyards.
The researchers point out that air pollution was highest in a wealthy area of Barcelona and that most of the schools in high-traffic areas that participated in the study are located there. Children attending schools where traffic pollution was lowest tended to have better-educated mothers, more siblings and fewer behavior problems than children attending schools in more polluted regions.
The researchers suggest the harms of air pollution could stay with children years into the future.
“Impairment of high cognitive functions has severe consequences for school achievement,” they write. “Thus, reduced cognitive development in children attending the most polluted schools might result in a disadvantage in mental capital, which may have a long-lasting life course effect.”
Outdoor air pollution
Air Pollution and Student Performance in the U.S.
Michael Gilraine and Angela Zheng. National Bureau of Economic Research working paper, May 2022.
Improvements in outdoor air quality over the past two decades have raised student test scores, according to this analysis, which also concludes cleaner air would help reduce longstanding differences in test scores between Black and white children.
To investigate the relationship between air quality and student achievement, the authors analyzed satellite-based measurements of fine particulate matter, or PM2.5, and other pollution-related data from 2002-03 to 2018-19. They then linked air quality data to math and reading test scores for more than 11,000 U.S. school districts for the academic years 2008-09 through 2017-18.
The authors also factored in schools’ proximity to power plants and year-to-year variations in production at individual plants.
They determined that concentrations of fine particulate matter dropped nationwide over the period studied, driven largely by reductions in coal use. For students, on average, PM2.5 concentrations dropped by 3 micrograms per cubic meter.
The authors point out that test scores, measured in standard deviations, rose, although not as much as they could have.
“Substantial improvements to student performance and equity through cleaner air are still possible, however,” they write.
- The U.S. Environment Protection Agency provides reports and resources on indoor air quality in schools, including national air-quality standards for particulate matter.
- The Indoor Air Quality Scientific Findings Resource Bank, located at the Berkeley Lab, gathers research on how indoor air quality affects people’s health or work performance.
- ASHRAE, formerly known as the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, is a professional organization with a mission of serving “humanity by advancing the arts and sciences of heating, ventilation, air conditioning, refrigeration and their allied fields.”
- The Indoor Air Program at the University of Tulsa conducts research on indoor air quality in schools, homes and workplaces.
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